Your subject line decides whether someone opens your email or scrolls past it. These 10 tips work for newsletters, promotions and sales emails, and each one comes with a before-and-after example.
1. Keep it short
Inboxes cut off long subject lines, especially on phones. Put the most important words first so the message still makes sense if the end is hidden.
2. Lead with the benefit
Tell the reader what they get. “Cut your weekly report time in half” gives a reason to open. “Our new reporting feature” does not.
3. Be specific
Numbers and details make a subject line believable. “3 SEO fixes for this week” beats “SEO tips”.
4. Use curiosity carefully
A little curiosity works when the email delivers on it. Vague teasers like “You won’t believe this” feel like spam and can raise complaint rates.
5. Personalise only when the email is personal
Adding a first name or company name can help, but only if the content inside is relevant to that person. A personalised subject line on a generic blast feels like a trick.
6. Write like a person
Plain, conversational wording often feels more natural than a headline written in capitals. Read it out loud. If it sounds like an advert, rewrite it.
7. Avoid spam-style formatting
Skip ALL CAPS, rows of exclamation marks and pushy phrases like “act now” or “100% free”. They annoy readers and can push emails toward the spam folder. Our email deliverability checklist covers the technical side of staying out of spam.
8. Use the preview text
The preview text appears next to or under the subject line. Use it to add detail, not to repeat the subject line.
9. Match the subject line to the email
If the subject line promises something the email doesn’t deliver, readers stop trusting your emails and start unsubscribing.
10. Test and keep notes
Most email tools let you A/B test 2 subject lines on part of your list. Test one change at a time and write down what wins, so you build your own list of what works for your audience.
Before and after examples
| Weak | Better | Why it works |
|---|---|---|
| Newsletter #42 | The email automation we set up this week | Specific and useful |
| Big sale!!! | Your 30% discount ends Friday | Clear offer and real deadline |
| Quick question | Question about Acme’s onboarding emails | Personal and relevant |
| Check out our webinar | How we cut churn by fixing onboarding (live, Tuesday) | Benefit plus date |
Subject lines matter most in automated emails that run for months, such as welcome emails. See our guide to 5 email automation flows every business needs.
